MRL-lpr/lpr disease: theories meet Fas.

It has been exciting for scientists to postulate all sorts of derangements to explain the numerous observations regarding the disease of MRL-lpr/lpr mice. Until recently, our imaginations have had almost free reign, unconstrained by any true knowledge. Now, however, it has been found that the lpr gene represents a mutation which causes a defect in a cell surface molecule, Fas. Since the normal Fas is thought to be important in programmed cell death, apoptosis, the lpr-associated defect in Fas is thought to interfere with normal apoptosis. Therefore, we are forced to reconsider all hypotheses regarding lpr/lpr mice in terms of a defect in Fas. This paper represents such an attempt. It suggests that failure of peripheral apoptosis of CD4+ cells allows self-reactive helper T cells to persist and drive autoantibody production. Failure of apoptosis of self-reactive CD8+ cells leads to down-regulation of CD8 and persistence as CD4-, CD8- T cells which contribute to the lymphadenopathy.